Opioids induce pharyngeal and esophageal dysfunction and reduce the lower esophageal sphincter (LES) pressure, and thereby decreases the barrier pressure between the stomach and esophagus. This contributes to an increased risk of regurgitation and aspiration during anaesthesia induction and in the postoperative period, when the patient is treated with opioids for pain relief. The effects of opioid antagonists on the opioid induced pharyngeal dysfunction and lower esophageal sphincter pressure are unknown. Therefore it is of great clinical value to evaluate if these negative effects are reversed by peripheral opioid antagonist, methylnaltrexone.